Few cars seem to have them. My current audi has, our Fiat has not.

In any case the current Römer Kid Plus just uses the belt.

Our previous Izi BeSafe was non-isofix, but it actually beat all isofix systems that year. To install it you have to push the seat down into the carseat with your weight (no problem for me), then pull the belt tight. Then you close the two ‘ears’ of the seat and the tention will keep the seat quite stable. Then you pull out a tab below the seat which tightens the belt even more.

Our first (and second replacement after the crash) was a Dremefa EasyBob (now out of production as the brand got bought by Bébécar) also had to be pushed into the car seat and then the belt had to be clamped by a plastic thing fixing the seat into the car. It proved quite effective.

I’ve been reading the instruction on URLs you’ve mentioned. What I find weird is that there is no mentioning of the ALR (Automatic Locking Retractor) / KISI (Don’t know how it’s spelled, but I think it’s short for kindersicherheit or something) mechanism that’s some of the retractors have specially for child seats.

This mechanism is usually activated when you pull out all webbing. When you feed back webbing you will hear a clicking sound, and you can’t pull out any webbing anymore. This can be used to make the webbing tight and stay tight. The mechanism will unlock when you feed enough webbing back.

You also might want to read:
http://www.cpsafety.com/articles/lockincss.aspx
http://www.carsafety4kids.com/lockingclip.html

Kurt

I’ve deleted all comments by fred@nerk.com and will delete all other comments that generate such bounces.

<fred@nerk.com>: host mail.nerk.com[72.9.249.29] said: 550 <fred@nerk.com> No such user here (in reply to RCPT TO command)

Without a third point the seat would rotate in a crash.

The main aim of this is to fix the child seat directly to the car, so we don’t depend on the seat (designed for an adult) to absorb the crash.

All the webbing I’ve seen stretches a lot. I think at 2500N it was in the order of 5 cm. But we don’t do any tests on the webbing itself. I’ve seen them, but never really took a close look at them.

On the other hand we did test on the buckle by putting up to 10kN on it, at which points it’s deformed but should still open. I wouldn’t want to use that one again.

Then you can also have up to 3 pretensioners for a 3 point seatbelt, as most cars have. Those can fire at different points. Those should pull you back in your seat. And I wouldn’t want to that with webbing that didn’t stretch.

Hopefully in a few years ISOFIX will take over. But at the moment it’s not viable in Australia.

http://hyperphysics.phy-astr.gsu.edu/hbase/seatb.html
Michael: If stretch isn’t a design criteria then it should be, see the above URL for the physics. Pre-tensioners are not to stop stretch, rather they are to take up the slack so that the seat-belt will start to slow the passenger as soon as they start moving forward in their seat (keeping them further away from solid things such as the wind-screen and allowing a stretching seat-belt to do more good).

It’s good that installation is free in the US! I’ll have to advocate a similar program in Australia.

Don: Good point, however as child seats aren’t sold with a car the combination of child-seat and car that you might purchase would almost certainly never have been crash-tested. Also there are no proper child crash-test-dummies, so any crash-testing has little relevance to children anyway.

Fred: 4WD and SUV vehicles are unsafe by design, and statistical analysis indicates that people who want to drive them have a lower opinion of their own driving skill than average. It’s not a rash statement, it’s well supported by scientific research. But it would break the flow if I cited references for everything in my posts. I’ll write some future posts about how unsafe 4WD and SUVs are. Sorry if you happen to own one, best to sell it now while the second-hand price is good…

Peter: Thanks for the detail. Am I correct in assuming that you agree with my claim that a child seat secured by several bolts is the ideal way to solve this problem?

Recent tests for EuroNcap showed that protection against front and rear collisions have improved a lot, the main weakness now seems to be side-impacts. That and improper use of the child seat of course. The main problem is not only attaching it to the car, but how strange it is to connect up the child.

To tighten the restraints I had to go into the car and pull with all my force until the space between the child and the belt to the recommended value of ‘one finger’. Of course that was why we only had slight injuries, and the baby none, while the other driver (without a seat belt) had to be reanimated…

In the US (Probably most of North America), all cars made after some date, now years in the past, must have hooks down in the seat and up behind the back that a car seat for children attaches to so the seat belt is not used at all (I believe it is called the latch system). The seats attach at two points on the back bottom sides and one point at the top middle.

Though it is true that the seat belt webbing is likely to stretch/degrade when used to restrain a person/object in an accident, it isn’t a design criteria. I.E. it’s not like a climbing rope that is designed to have elasticity so as not to break your fall suddenly. In fact, our current car has a ’seat belt pre-tensioner’ that fires a charge that actually puts a great deal of force on the seat belt retracting as much as possible in the event of an accident. This is controlled by the same mechanism that fires the air bag though with a lower threshold for impact speed required to trip it. So it is possible for the pre-tensioner to fire but not the airbag, I believe the set points are in the neighborhood of 20 and 25 mph though it has been some time since I’ve looked in the manual.

Lastly, professional installation of a car seat (or verifying proper installation of an already placed car seat) in the US is free and as simple as traveling to the local fire department. Fire departments usually have periodic car seat safety drives. Before moving to NJ I was a volunteer fire fighter and there were a few times someone came by the firehouse for help with a new car seat or to see that they had put theirs in right. In fact, when my wife and son were released from the hospital, one of the nurses had to come to the car with us and see that the car seat was the right size/installed properly. This actually was a bit of a pain as my son was premature and thus smaller then normal. Had to go and get an insert so that the seat properly held him,